The present invention relates to a process and apparatus for post-treatment of a metal strip by spraying the metal strip with a rinsing liquid to prevent staining when the strip is stopped. More particularly, the invention relates to a rinsing process where the metal strip is completely covered with liquid when the metal strip is at a standstill. In addition, the invention refers to a device for implementing the process.
The pickling of steel is a process for removing scale from the surface of the steel that is present after various forming operations. Continuous sheets of steel are typically carried through several acid baths by immersing the strip completely in the baths for sufficient time to remove the scale. It is necessary to remove the acid residue from the steel after the pickling step to prevent corrosion, staining or spotting of the surface.
Pickling plants for treating a continuous steel strip usually include a strip rinsing facility downstream of the acid pickling stage in order to remove any residual pickling acid still adhering to the surface of the strip as the strip exits the pickling section. This rinsing process can be implemented by spraying the rinsing liquid directly onto the strip. Alternatively, the strip can be rinsed by pulling the strip through a bath of the rinsing liquid. In plants where the rinsing liquid is sprayed through nozzles directly onto the strip, the strip surface suffers serious discoloration due to oxidation if the air and rinsing water are allowed to act on the strip simultaneously during prolonged stoppages of the strip movement through the rinse station. In order to alleviate this situation, it has been suggested that the rinsing liquid be applied through nozzles and that the station be flooded with the rinse liquid when the forward movement of the strip is interrupted. The station is flooded to a level to completely cover the steel strip, thereby preventing oxygen from contacting the steel strip during the stoppage. Complete immersion of the strip reduces the staining on the strip when the strip is stopped.
Such processes and devices are known, for example, in AT 404 472 and EP 788 843. These patents disclose closing a drain valve of the rinsing tank when the strip comes to a standstill. As a result, the rinsing tank fills up to an overflow edge located above the strip. The disadvantage here, however, is that it takes a relatively long time for the tank to fill, and thus, oxidation may still occur on the strip surface before the strip is completely immersed in the rinse liquid.
In order to remedy this disadvantage, EP 788 843 discloses re-routing the rinsing liquid feed from the nozzles to an inlet specially provided for this purpose when the strip comes to a standstill. Nevertheless, the time elapsing before the rinsing tank has filled is also fairly long in this case, thus the risk of discoloration due to oxidation remains.
The present invention is directed to a process and apparatus for rinsing a metal strip of material passing through a rinsing station while preventing corrosion and staining of the metal strip. More particularly, the invention is directed to a process and apparatus for spraying a rinse liquid onto a continuously moving metal strip and flooding the rinse station during stoppage of the advance of the metal strip. The rinse station is flooded quickly to cover the strip and prevent oxidation.
Accordingly, a primary object of the invention is to provide a process and apparatus for rinsing a metal strip while reducing the risk of oxidation and staining of the metal strip.
Another object of the invention is to provide a process and apparatus for rinsing a strip material and flooding the strip material with a rinse liquid using equipment that is economical and easy to assemble.
Another object of the invention is to provide a process and apparatus for rinsing a strip material with a rinse liquid where the advancing movement of the strip material is monitored and where the rinse station is quickly flooded with the rinse liquid when a stoppage of the strip material is detected.
A further object of the invention is to provide a process and apparatus for rinsing a strip material by spraying a rinse liquid onto the moving strip material and quickly immersing the strip material in a pool of the rinse liquid when the strip material is at a standstill.
Still another object of the invention is to provide a process and apparatus for rinsing a strip material by carrying the strip material from an inlet end to an outlet end of a rinse tank and closing the inlet and outlet ends of the rinse tank when the strip material is at a standstill to form a pool of the rinse liquid in the rinse tank and to immerse the strip material in the rinse liquid.
A further object of the invention is to provide a process and apparatus for rinsing a strip material by carrying the strip material between spaced apart pinch rollers in a rinse tank and closing the gap between the pinch rollers and the rinse tank when the strip material is at a standstill to prevent drainage of the rinse liquid in the tank and to form a pool and immerse the strip material in the rinse liquid.
Another object of the invention is to provide a process and apparatus for rinsing a strip material by spraying a rinse liquid in a rinse tank where the rinse tank has a relatively small volume so that the rinse tank can be flooded and the strip material can be immersed in the rinse liquid quickly when the strip material is at a standstill.
Still another object of the invention is to provide a process and apparatus for rinsing a strip material in a spray rinse tank having pinch rollers at an inlet end and an outlet end and pneumatically operated seals for closing a gap between the pinch rollers and the rinse tank to present draining of the rinse tank and to flood the strip material in a pool of the rinse liquid.
A further object of the invention is to provide a process and apparatus for rinsing a strip material by passing the strip material through a spray rinse tank having pinch rollers at an inlet end and an outlet end and hydraulically operated seals for closing a gap between the pinch rollers and the rinse tank to prevent draining of the rinse tank and to flood the strip material in the rinse liquid.
Another object of the invention is to provide a process and apparatus for rinsing a steel strip material by carrying the strip between opposing pinch rollers for supporting the strip and providing a rinse tank having a bottom wall closely spaced to the strip and extending between the pinch rollers for defining a flooding zone.
A further object of the invention is to provide a process and apparatus for rinsing a strip material in a spray rinse tank having a detector for detecting the speed of the strip material passing through the rinse tank and a delay mechanism for flooding the rinse tank with a rinse liquid after a predetermined time period after the strip material has come to a standstill.
A further object of the invention is to provide a process and apparatus for rinsing a steel strip in a spray rinse liquid about 5 seconds to about 2 minutes after the advance of the strip is stopped.
Another object of the invention is to provide a process and apparatus for rinsing a strip material having a plurality of spaced rinse tanks and a pair of pinch rollers positioned between adjacent rinse tanks for supporting the strip material where the rinse tanks have movable seals for contacting the pinch rollers to close the rinse tanks and form a pool to immerse the strip material in the rinse liquid.
These and other objects of the invention are basically attained by providing a process for rinsing a strip material comprising: feeding a strip material through a rinse station, spraying a rinse liquid onto the strip material within the rinse tank; and detecting a stoppage of the strip within the rinse station and closing the inlet and outlet of the rinse tank to form a rinse liquid pool in the rinse tank having a depth to immerse the strip material in the rinse tank during the stoppage. The rinse station has a rinse tank with an inlet for receiving the strip material and an outlet for discharging the strip material.
These and other objects of the invention are further attained by providing a process for rinsing a strip material, comprising: continuously feeding a strip material through a rinse tank, continuously spraying a rinse liquid onto the strip material carried through the tank; detecting a stoppage of the strip material being carried through the rinse tank; and closing the gap between the tank and the first and second pairs of pinch rollers to form a rinse liquid pool in the tank having a depth to immerse the strip material in the tank during the stoppage. The rinse tank has an inlet for receiving the strip material and an outlet for discharging the strip material. The rinse tank further has a first pair of pinch rollers disposed in the inlet and spaced from the tank to define a gap, and a second pair of pinch rollers disposed at the outlet and spaced from the tank to define a gap. The strip material is carried by the first and second pinch rollers through the tank.
The objects of the invention are still further obtained by providing a rinsing apparatus for rinsing a continuously advancing strip material. The apparatus comprises a rinse tank having an inlet for receiving a strip material, and an outlet for discharging the strip material. A plurality of spray nozzles are positioned in the rinse tank for supplying a continuous spray of rinse liquid onto the strip material within the rinse tank. A first sealing device is coupled to the inlet of the rinse tank and a second sealing device is coupled to the outlet of the rinse tank. The first and second sealing devices are positioned to close the inlet and outlet and cause the rinse liquid to pool in the rinse tank to a level to immerse the strip material in the rinse liquid.
The objects of the invention are yet further obtained by providing a rinsing apparatus for rinsing a continuously advancing steel strip. The apparatus comprises a plurality of rinse stations arranged in a direction of travel of the advancing steel strip. Each of the rinse stations comprises a rinse tank having an inlet for receiving the steel strip and an outlet for discharging the steel strip. A plurality of spray nozzles direct a spray of rinse liquid onto the steel strip. First upper and lower pinch rollers are at the inlet end of the rinse tank and define a first gap therebetween. Second upper and lower pinch rollers are at the outlet of the rinse tank and define a second gap therebetween. A first sealing device is coupled to the inlet of the rinse tank for closing the first gap. A second sealing device is coupled to the outlet of the rinse tank for closing the second gap. The first and second sealing devices selectively close the first and second gaps to cause the rinse liquid to pool in the rinse tank to cover the steel strip.
The objects, advantages and other salient features of the invention will become apparent from the following detailed description of the invention and the annexed drawings which form a part of this original disclosure.